Quantitative mRNA and Protein Analyses of ZPB1, ZPB2, and ZPC in Different Genetic Strains of Broiler Breeders

Abstract

The avian inner perivitelline layer (IPVL), containing the zona pellucida (ZP) family of proteins, surrounds the ovulated ovum. Sperm binding at the germinal disc (GD) region of the IPVL initiates fertilization in avian species, and the amount of sperm binding at the GD reflects female fertility. RT-PCR and quantitative Western blot analyses were used to determine differences in ZP protein mRNA expression and protein concentration between GD and nongerminal disc (NGD) regions among four genetic strains of broiler breeders. Both the mRNA expression and protein concentration of chicken ZPB2 was greater in the GD region, compared to the NGD region, and ZPB2 protein was more abundant in the small prehierarchical follicles. Chicken ZPC mRNA, but not ZPC protein, was greater in the NGD region compared to the GD region, and hepatically expressed ZPB1 protein was more concentrated in the NGD region. Testosterone increased the expression of both ZPC mRNA and protein in cultured granulosa cells from prehierarchical follicles. The current research is the first to investigate the relative amount of ZP proteins between the GD region and NGD region in chicken IPVL. The results provide further evidence that ZPB2 may be critical for avian sperm binding at the GD region of the IPVL.